1) Field of the Invention
The present invention relates to a method of and an apparatus for lapping a magnetic head slider, and more particularly, to a method of and an apparatus for lapping a magnetic head slider that further enhances lapping precision and prevents formation of a scratch or a smear in gaps of magnetoresistive (MR) elements or electrical lapping guide (ELG) elements.
2) Description of the Related Art
Recently, with increase in capacity of a hard disk drive, it is required to reduce a size and a width of a track and a gap of a combined type magnetic head having a slider. Since a thin magnetic film becomes more popular, precise control with excellent productivity is required also in lapping process of the magnetic head slider.
Generally, in a conventional working process of the magnetic head slider, since a row bar in which a plurality of magnetic head elements are aligned in a line is cut out from a wafer and the cut out row bar is lapped into a desired size, the row bar is pushed against a lapping plate under a predetermined pressure and the row bar is lapped.
FIG. 20 is a schematic diagram of a row bar as viewed from a surface of the row bar to be lapped. That is, on the row bar 10, magnetic head sliders 11 and work-monitoring resistive elements, electrical lapping guide (ELG) elements 12, are alternately arranged. Each of the magnetic head sliders 11 comprises an alumina section 13 and an alumina carbonized-titanium section 14. The alumina section 13 includes an upper magnetic pole 15, an upper shield (lower magnetic pole) 16, an MR film 17 and lower shield 18.
As means for precisely lapping such a row bar 10, the present inventor, for example, proposed a lapping method and a lapping apparatus disclosed in Japanese Patent Application Laid-Open No. 2001-162526. A lapping direction component of the row bar 10 by this lapping apparatus will be explained with reference to FIG. 21. FIG. 21 is a schematic diagram of the lapping direction component as viewed from the surface of the row bar to be lapped. FIG. 21 depicts the surface 10a of the row bar 10 to be polished and a turning and oscillating center 19 of the row bar 10. A lapping direction component and a surface plate rotation direction are shown with arrows in FIG. 21.
The lapping apparatus includes a rotating lapping plate, first oscillating mechanism which simply primary oscillates the mounted row bar 10 such that the row bar 10 reciprocates in the radial direction of the lapping plate, and a second oscillating mechanism which turns and secondary oscillates the mounted row bar around itself. A oscillating period of the row bar by the first oscillating mechanism and a oscillating period of the row bar by the second oscillating mechanism are set differently so that the row bar is oscillated in a combined manner.
According to a lapping method by means of this lapping apparatus, the row bar is subjected to a rough lapping first by the simple oscillating and then by the combined oscillating. A resistance ELG-R of the work-monitoring resistor is monitored, and the ELG-R is converted into an MR element height MRh. If the converted value MRh reaches a predetermined value, a supply of coarse slurry is stopped, finishing slurry is supplied, and the row bar is subjected to a finishing lapping by means of the combined oscillating. During the lapping operation, the working pressure and the rotation speed of the lapping plate are reduced in accordance with the proceeding state of the lapping based on the converted value MRh.
In the lapping operation by means of the combined oscillating, the row bar 10 is always moving, there is no moment at which a relative speed between the lapping plate and the surface 10a of the row bar 10 to be polished becomes zero. Therefore, a lapped surface is not scratched by the lapping plate. Further, since the lapping direction is not uniform, the row bar can be lapped uniformly and precisely.
Recently, however, gaps, for example, between the MR film 17 and the lower shield 18 of the MR elements of the magnetic head slider 11 or the ELG elements 12 are extremely small, and if the finishing lapping using the combined oscillating is carried out, there is a problem that scratches or smears are formed in the gaps, and the sensitivity of the element may be deteriorated due to a short circuit or the like.